Leukocytes adhere to and migrate through the endothelium using specific cell adhesion molecules (CAM's) that are expressed in a programmed and sequential manner. Because the inflammatory response occurs in the context of shear stress, cytokines, chemoattractants, extracellular matrix structures, and the presence of multiple cell types, in vivo models are needed. The overall goal of this proposal is to develop new in vivo models that will allow study of human endothelial cell-leukocyte interactions, This will allow the use of many of the anti-CAM antibodies developed in human cell culture models that do not cross-react with animal CAM's and address the problems in extrapolating animal findings to humans. To accomplish this, pieces of normal human skin have been transplanted onto immunodeficient (SCID) mice. Immunohistochemical analysis has revealed that these human skin grafts closely resemble normal skin, maintain their human vasculature, have the ability to upregulate CAM's such as E-Selectin and ICAM-1, and have the ability to support an active inflammatory reaction with migration of murine leukocytes into cytokine- injected areas. Our specific aims are to: 1. Further characterize the human skin/SCID model with regard to: A. the in vivo regulation and kinetics of expression of endothelial cell adhesion molecules (including P-Selectin, E-Selectin, ICAM-1, VCAM-1, and PECAM-1) during inflammatory reactions induced by selected cytokines, chemoattractants, endotoxin, bacterial infection, and mast cell degranulation. B. Determine which cytokine or cytokine/chemoattractant combinations are necessary for white blood cell (both murine and human) migration into tissues. 2. Use specific bioactive antibodies against human endothelial cell adhesion molecules and carbohydrate mimics of CAM ligands to determine the functional role of endothelial cell CAM's in leukocyte infiltration with special attention to E-selectin and a novel vascular adhesion molecule, PECAM-1. 3. Define parameters that control the ability of specific types of injected human white blood cells (i.e neutrophils vs eosinophils vs lymphocytes) to be targeted to specific types of inflammatory reactions. 4. Characterize a second type of microvascular bed by development of a new human/SCID chimera utilizing transplanted human bronchial tissue. These studies will lead to an enhanced understanding of the biology of leukocyte-endothelial cell interactions in human in situ microvessels. This information, along with the ability to test the ability of specific agents to induce or inhibit leukocyte emigration in a human in vivo model, will be extremely useful in designing novel therapeutic agents.